Turbocharging an engine allows the engine to provide power similar to that of a larger displacement engine. Thus, turbocharging can extend the operating region of an engine. Turbochargers function by compressing intake air in a compressor via a turbine operated by exhaust gas flow. Under certain conditions, the flow rate and pressure ratio across the turbocharger can fluctuate to levels that may result in noise disturbances, and in more severe cases, performance issues and compressor or turbine degradation.
Such turbocharger performance issues may be mitigated by adjusting the flow rate through the turbocharger, such as by adjusting one or more turbocharger bypass valves. However, such adjustments may not provide adequate avoidance of the flow rate/pressure ratio fluctuations, or may compromise power, fuel economy, and/or emissions.